Back in 1999, a computer scientist at Cornell University began monitoring the way that the Windows NT 4.0 operating system used files. What he found was astonishing.

About 80 per cent of all files that NT creates are either over-written or deleted within 5 seconds of being born.

Today, Ragib Hasan and Randal Burns at Johns Hopkins University in Baltimore say this ought to give programmers pause for thought. Deleting data requires energy, which means that a substantial fraction of a computer system’s energy budget is currently devoted to creating and then almost immediately scrubbing data.

And if the wasted energy weren’t bad enough, computer memory has a limited life span. Flash memory, for example, has a lifespan of 100,000 cycles. So cycling it needlessly brings the inevitable breakdown closer.